


Size Matters

by FuryRed



Series: Heart and Soul [5]
Category: X-Men (Alternate Timeline Movies), X-Men (Movieverse), X-Men - All Media Types
Genre: Alternate Universe - College/University, Alternate Universe - Still Have Powers, Charles Xavier has a Ph.D in Adorable, Domestic Bliss, Erik's Sizeable Obscenity, Established Relationship, I can't believe there's a tag for that already..., Idiots in Love, M/M, Penis Measuring
Language: English
Status: Completed
Published: 2017-06-24
Updated: 2017-06-24
Packaged: 2018-11-18 11:38:20
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,950
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11289954
Author URL: https://archiveofourown.org/users/FuryRed/pseuds/FuryRed
Summary: They say size isn’t everything, but Charles is determined to find out if that’s true... FOR SCIENCE.





	Size Matters

**Author's Note:**

  * For [pinkoptics](https://archiveofourown.org/users/pinkoptics/gifts).



> I know I said I wouldn't write this but I couldn't help myself.
> 
> THIS IS SO DUMB I'M SORRY

 

 

In the time during which Erik has known Charles, he has become accustomed to the frequent displays of Charles’ curiosity.

Erik knows that, as a scientist, Charles is never happier than when he is embroiled in one experiment or another- be that within the scope of his studies or in his leisure time. Over the past several months Erik has helped Charles out on numerous occasions with his research, joining Charles in the university labs as he allows Charles to fully explore every facet of his mutation, and never tiring of the way Charles’ eyes grow bright and excited with every display of Erik’s power.

Of course, not all of Charles’ experiments are so much fun to take part in, or to witness…

There is the time when Charles conducts a sleep study, and Erik has to put up with Charles all tired and grumpy for three days as he attempts to stay awake longer than his co-researchers, culminating in the point when- after Charles has decided that _distraction_ is the best way to fight fatigue- he has been busy trailing his mouth along the inside of Erik’s thigh, until suddenly the movement stills and Erik looks down to find Charles fast asleep with his face pressed into Erik’s lap.

There is the time when Charles insists that he has created a device to increase the scope of Erik’s mutation- to enable him to reach further and command more with his power than ever before. It’s a good idea, but the actual result is distinctly unimpressive... Instead of amplifying Erik’s powers of metal manipulation, the device instead seems to turn him into a giant magnet, and for a day and a half Erik finds he cannot come into contact with metallic items without them sticking to his skin- much to Charles’ surprise (and barely concealed amusement). Erik spends the time waiting for the effects of the device to wear off, scowling, and trying not to smile at Charles who at one point decides to see how many spoons he can balance on his own face to compensate for Erik’s condition.

But occasionally, Charles’ experiments have a tendency to be rather more worrying than comedic... There is the time when Charles and his lab partner Hank begin creating some sort of machine to increase Charles’ telepathic ability, something that Erik regards with scepticism and concern given how it reminds him of certain variants of manipulative equipment he has come into contact with in his own life. Erik watches as Charles stands in the centre of a small room wearing what looks like a colander on his head with various wires coming out of it, his face joyfully excited as he smiles at Erik, whilst meanwhile Erik mentally runs his powers over all the metal in the room- ready to tear it to the ground should Charles show any signs of discomfort.

To begin with it seems like the device is working, and that ‘Cerebro’ is operating as it is supposed to, but then Charles lets out a yelp of surprise falls to his knees, and before Hank can even reach to turn off the device Erik is sending a magnetic pulse through it, causing bulbs to explode and wires to crackle as Erik drops to his knees beside Charles and pulls him into his arms.

After that particular experiment Charles insists that he is fine, that it was just a minor setback that damaged his hair and nothing else, and that any future research will progress more smoothly. Erik still harbours doubts, and holds onto Charles’ hand a fraction too long when he drops him off at the lab the next day. In the end though, Erik knows that Charles is not one to be restrained, that to try to stop him from expanding his mind to the fullest would be stifling, and so he tries to keep his concerns to himself and to just be supportive.

But of course, some of Charles’ experiments require a little more support than others…

 

“Darling, can I measure your cock?”

At the words Erik jumps, looking down at where Charles is lying next to him, at where Charles was moments ago stroking his hand up the length of Erik’s large cock where it rests against his stomach. There is a look in Charles’ eyes that Erik has become accustomed to- a look of curiosity and wonder as he smiles sweetly up at Erik, before he draws his thumb slowly over the head of Erik’s member to make him groan.

“Charles, what--” Erik is lost to another helpless murmur as Charles dips his head down, mouthing up the length of Erik’s shaft as he cups Erik’s balls in one hand. For a while Erik forgets all about what Charles has just asked- too consumed with the feeling of Charles’ lips on his member to think about much else as he shuts his eyes and moans- but then there is something other than the feel of Charles' hands and mouth against his skin, and Erik glances down and sees the tape measure that Charles is now grasping in one hand.

“Charles!” Erik exclaims, edging back slightly on the mattress as Charles attempts to line up the tape measure before Erik bats it away. “Stop that”, he scolds.

Immediately Charles’ expression grows pleading, his lower lip forming a pout that Erik can’t help but find irresistible. Well, usually…

“Charles, I’m not letting you measure my cock…”

“Why not?” Charles whines, placing the palm of his hand on Erik’s chest and rubbing the surface in circular motions, the tape measure still clutched between the fingers of his other hand.

“Because… because it’s ridiculous. Why on earth would you even want to?”

Charles shrugs. “For science. There’s a theory that there’s a correlation between the distance from your thumb to the tip of your forefinger and the length of your cock, and I just want to see if it’s true. Purely for research purposes, of course…”

“Well, why don’t you measure your own?” Erik asks, reaching down to stroke one hand through Charles’ hair, and feeling where the ends are still slightly singed from Charles’ ill-advised experiment with Cerebro.

Immediately Charles’ expression slips into a sly smirk. “Well, darling- it’s clear that you’re a significantly more _impressive_ test subject than I am…” he says with a wink. “And besides, in order to have a conducive experiment it’s important to ensure a wide range of research material is available, and that numerous participants are used”.

“Charles, are you trying to tell me that you’ve been going all over campus measuring different cocks…?”

“No, darling”, Charles laughs. “I’m just saying that I need more than just myself in order to provide a suitable basis for a theorem”.

“Is that so…?” Erik asks, rubbing one thumb against Charles’ jawline as he gazes down at him. Charles looks so beautiful- from Erik’s position he can see the stunning spectrum of freckles that span Charles’ back, running down his spine and leading to his glorious arse- round and firm, with a small birthmark in the shape of tiny heart at the top of his right buttock. The issue of the tape measure is still one that Erik wants to address, but for now he finds he is rather more distracted by the sight of Charles lying naked next to him, particularly given the knowledge that Charles is already lubed and ready for sex...

“Come here…” Erik murmurs, sliding his hands down to hold Charles’ waist and using his grip to manoeuvre Charles on top of himself. Charles rolls on top easily- spreading his legs to place his knees either side of Erik’s thighs, and pressing his torso against Erik’s as he smiles softly and leans down to kiss him.

As they kiss Erik trails his fingertips down Charles’ spine, eliciting little moans and shudders from Charles- each one like music to Erik’s ears, warming his heart and soul. In time Charles winds his arms around Erik’s neck- the tape measure thankfully forgotten- and rolls his hips forward during the embrace, causing his cock to slide along the space between both their stomachs as Charles groans into Erik’s mouth. It’s glorious, but Erik wants more. And so, he reaches down to grasp his own cock and lines it up with Charles’ arse, but stops short of pushing inside.

Charles can’t tell of course, considering their mouths are still pressed together, but a sly grin has begun to creep over Erik’s face, and as he pushes the head of his cock against Charles’ hole he moves his mouth over to Charles’ ear and murmurs: “Tell me, Charles- how many inches is this?”

The noise that Charles makes as Erik pushes inside is probably worth the subsequent slap against Erik’s chest, and Erik can’t help but chuckle as his cock slides approximately halfway in and Charles curses under his breath. Of course, Charles isn’t one to just let Erik get away with misbehaving, and he sucks in an untidy breath before he replies: “Mm, I don’t know, Erik- I can’t really feel anything…”

“Hey!” Erik protests, smacking Charles on the arse and trying not to laugh in spite of himself, an objective made all the more difficult when Charles leans back and Erik gets a look at his flushed cheeks and the mischievous grin on his face.

“I think my theory was wrong”, Charles continues, squirming as Erik quickly diverts his attention towards tickling Charles’ ribs. “There’s no correlation. Science is a lie!” He attempts to wriggle out of Erik’s grasp, in spite of the fact that he is still being penetrated, but is eventually stilled by Erik sliding both hands to hold the back of Charles’ neck and pulling him closer, so that their faces are inches apart.

“Tell me when you feel something…” Erik murmurs. With that, he pushes his cock all the way inside, watching Charles’ face tense with pleasure as he moans and grips Erik’s arms with both hands. Charles doesn’t need to say anything, just the way he is breathing hard and trembling is evidence enough, but after Erik’s member is buried to the hilt Charles settles down, smiles at Erik, and whispers: “Darling, you’re so big…”

It probably goes without saying, but Erik appreciates the little boost to his ego nonetheless. Compliments from Charles are always easily given but still completely valued- each one a little gesture that warms Erik’s heart, and Erik doesn’t ever think he will ever be able to thank Charles enough for the care and sentiment he offers with every part of himself.

Using his grip on the back of Charles’ neck Erik pulls him closer to touch his lips to Charles’ mouth, at the same time using the techniques Charles has taught him to gently press his affection into Charles’ mind in a mirror of the same kiss. Erik can feel Charles smiling even if he can’t see it, the feeling like golden rays of warm sunlight brightening his mind as Charles closes his eyes and hums contentedly against Erik’s mouth.

For a while Erik is just happy to hold Charles’ around the waist as he thrusts into him, sliding his cock in and out with aching slowness as Charles moans softly and moves to rest his head against Erik’s shoulder, his fingertips drawing gently through Erik’s hair. Against his stomach Erik can feel the hardness of Charles’ cock there, sliding forward with each of Erik’s thrusts, flushed and desperate to be touched. The groan that Charles lets out as Erik wraps one large hand around Charles’ member betrays the desperation Charles is feeling, and Charles turns his face further into Erik’s shoulder and gasps: “Yes… yes, darling…”

For someone as calm and composed as Charles usually is, it’s amusing to Erik just how woozy and lust-stupid Charles can get during sex. It’s like Charles ascends into some other kind of mental headspace when they are in bed together, most likely due to the fact that the barriers he uses to keep his telepathy in check are often steadily eroded with each languid thrust of Erik’s cock. Erik loves it. To him, nothing is more beautiful than the feeling of Charles’ mind slowly wrapping itself around his own, filtering into his senses and joining the two of them in heart, body, and soul. Sometimes it’s hard for Erik to keep control of his own faculties, to not just fall into Charles and linger in that happy dream-space forever, but usually the physical feeling of Charles’ body next to his own is enough to keep Erik grounded, particularly when he has a point to prove…

Erik watches Charles’ face carefully, seeing that his eyes are closed and his mouth is gaping slightly as his body rocks forward with each of Erik’s thrusts. Considering he is suitably distracted it’s no surprise that Charles doesn’t immediately notice as Erik reaches to pick up the tape measure Charles previously discarded, not until the point Erik lines it up with Charles’ cock and Charles lets out a small shriek.

“Erik!” Charles exclaims, eyes snapping open as he sits back, inadvertently pushing Erik’s cock deeper into his ass and causing Erik to let out a groan as his fingers fumble with the tape measure. “What are you doing??” Charles demands.

“I’m helping you with your experiment”, Erik smirks, holding Charles’ member in one hand as he attempts to line up the tape measure with the other.

“Nooooo!” Charles whines, wriggling on top of Erik and slapping at his hands. “I only wanted to measure yours, not mine”.

“You said it yourself, Charles- multiple test subjects…”

“Well I didn’t mean it!” Charles hisses, the indignant expression on his face only making Erik’s grin wider. Charles is adorable when he pouts, and Erik is close to abandoning this little endeavour in favour of just pulling Charles close to kiss him instead. However, this is what Charles wanted, after all, and Erik can’t just give up on science…

“Hold still”, Erik requests, pressing his palm against Charles’ chest to steady him. There is a low whine from Charles but he complies, and his protests turn into a low grumble as he sits still and allows Erik to measure him. Once he is finished Erik drops the tape measure back onto the bed, and places the palms of both hands against the warm skin of Charles’ thighs as he looks up at him.

“There”, Erik smiles. “That wasn’t so bad, was it?”

“I doubt it was worth the effort…” Charles mutters, and finally Erik understands why Charles is sulking quite so emphatically.

“Liebling…” Erik says softly. “You’re not feeling inadequate, are you?”

Charles shrugs, chewing on his lower lip as he continues to stare down. “Have you _seen_ the size of your cock? How could I not be?”

“Liebling…” Erik says again, reaching up to brush his thumb along Charles’ jawline. “Six inches is nothing to be ashamed of, and I can assure you it’s more than enough for me”.

With that, Erik transfers one hand to grasp Charles’ member, stroking along the length of it and smiling as Charles’ eyelids flutter in response to the sensations.

“Trust me, Charles- I doubt I could get much more in my mouth”.

“You can barely get it in your mouth as it is…” Charles replies, the corners of his lips drawing up in a devious smirk.

“Oh, is that so?” Erik laughs, playfully squeezing Charles’ cheek. “Well, I guess we’ll see about that…”

At that, Erik moves both his hands to grasp Charles’ hips and pulls him forward, letting out a quiet groan as his cock slips out of Charles’ arse that is matched by Charles’ own soft moan.

“Erik, what--?” Charles starts, but when he is suitably positioned kneeling over Erik’s torso Erik reaches once more to grasp Charles’ member and brings it to his lips, and Charles understands what Erik is planning.

“You just can’t turn down a challenge, can you sweetheart?” Charles smiles, stroking his fingers affectionately through Erik’s hair.

The zealous grin Erik flashes at Charles is an answer in itself, and his smile only fades as he rubs his lips against the sensitive head of Charles’ cock, before opening his mouth and taking Charles in.

Erik keeps his eyes focused on Charles as he sucks on his cock, gazing at the smooth planes of muscle that span Charles’ chest and abdomen trembling with pleasure, watching the expression in Charles’ eyes that in that moment are deep blue and almost completely dilated. There are breathy little gasps that escape Charles’ lips as Erik slides his mouth up and down Charles’ cock, until the point when Erik carefully takes the full length in, and sends a pointed _“Told you so”_ at Charles when it happens.

 _“I’ve never been more happy to be wrong”_ , Charles sends back, accompanied by the feeling of a kiss that Erik feels in his mind. But although Erik is happy to have proven himself, he’s lacking in the certain _skill_ that Charles possesses in this particular department, and he can only keep Charles’ cock deep in his mouth for a short while before he has to withdraw to focus on the top couple of inches once again.

Nevertheless, Charles seems happy with Erik’s efforts, and he smiles down at Erik and whispers gentle encouragement as Erik continues to suck. As he continues with his motions, Erik slides his hands around to hold Charles’ arse, trailing the fingertips of one hand down the crease between Charles’ buttocks. Erik can feel Charles tense and senses the impression of a question from his mind as Erik traces the sensitive area around his entrance, but there is no protest and so Erik continues with his rhythm as he slips his fingers steadily inside Charles’ still-lubed hole.

The noise that Charles makes as Erik wriggles his fingers inside and seeks out Charles’ prostate is heavenly, a low hum of pure pleasure punctuated by heady gasps as a result of the dual attention. Of course, Erik only realises just _how_ much Charles is enjoying himself when he gives Charles’ prostate a thorough stroke, Charles groans, and his hips rock forward to send his cock deeper into Erik’s mouth.

Immediately Charles recovers and straightens up, stroking Erik’s hair somewhat frantically and sending him a sincere: _“Sorry, love, sorry sorry sorry”_ , whilst meanwhile Erik feels his own arousal deepen in response to Charles’ unexpected thrust, causing his cock to leak pre-come onto his stomach. Normally Charles is rather passive in bed- always eager to engage but allowing Erik to take the lead in directing the nature of their intimacies- and Erik is surprised to realise that he actually quite likes the idea of Charles being in control, of Charles being commanding, of Charles taking the lead for once.

_“Fuck my mouth, Charles”._

As soon as Erik has sent the thought he can tell it’s been received by the way Charles sucks in an unsteady breath and his whole body tremors. There’s uncertainty in his eyes, and trepidation, but Erik only gazes up at Charles, his mouth still enclosed around Charles’ hard cock, gives his arse cheek an encouraging squeeze, and hopes Charles can tell how much he really does want this.

Though Charles’ hands flex uncertainly in Erik’s hair for a moment, eventually he draws in a deep breath and rolls his hips back, before thrusting forward into Erik’s mouth. At first Charles’ movements are slow and hesitant, but as Erik begins to brush his fingers against Charles’ prostate once more he lets out an impassioned moan and begins to move more vigorously, causing great swells of pleasure to flow over Erik like waves crashing down. Erik can feel Charles’ enjoyment cresting over him, but more than that he can just feel his own pleasure, his own arousal at seeing and feeling Charles so uninhibited and assertive. It’s startling given how much of the early part of their relationship involved Erik basically taking his pleasure from Charles, but to Erik there is suddenly nothing hotter than having Charles fuck his mouth.

Though Charles is clearly consumed by pleasure he is still considerate above all else, and he does not push Erik for too much. Regardless, it doesn’t take much anyway- the twin attention of Erik’s mouth on his cock and Erik’s fingers in his arse is enough to have Charles shaking and moaning desperately, until he lets out a final heated groan and he comes in Erik’s mouth. Erik holds Charles as he comes, keeps his finger pressed against Charles’ prostate, keeps his mouth open for Charles to thrust into. Eventually Charles settles down, and he shuffles backwards on shaky legs until he lies down flat against Erik’s chest with his face pressed into the curve of Erik’s collarbone.

For a while it is quiet, nothing but the sound of fading moans and laboured breathing in the air, but eventually Charles turns to snuggle his face into Erik’s neck, and murmurs: “Thank you…”

Erik smiles. “I would say ‘the pleasure was all mine’, but that’s not entirely true”, he replies, smoothing his hands gently up and down Charles’ back. Erik’s cock is still desperately hard- more so after seeing and feeling Charles’ pleasure- and the heat of Charles’ skin against Erik’s member makes him ache for closer contact. But Charles is only just coming down from, well, _coming_ , and Erik doesn’t want to ask him for anything too taxing, so he simply grasps hold of Charles’ ass with both hands, and begins to slide his cock along the line of Charles’ buttocks.

“Is this alright, Schatz?” Erik murmurs, tilting his head to whisper in Charles’ ear.

“Mmm…” Charles replies, wriggling his hips to line his arse up more securely with Erik’s cock, providing glorious friction for Erik as he starts to thrust in earnest.

After such a dizzying encounter so far it doesn’t take long before Erik feels like he is teetering on the edge of climax, something that Charles must clearly be able to perceive too as he lifts his head from Erik’s shoulder and begins to trail love-drunk kisses over Erik’s jawline and towards his mouth.

“In me…” Charles whispers against Erik’s lips.

With Charles’ permission granted, Erik positions his cock at Charles’ entrance and pushes inside, only needing a few more thrusts until he comes with a heady groan. Charles watches his face as it happens, a contented smile lifting the edges of his mouth, until Erik stills and Charles dips his head to press a single, simple kiss to the tip of Erik’s nose.

 

The next morning, Erik awakens to the sight of Charles’ head beneath the bedsheets.

The previous night had been spent watching television with Charles until they were both tired, at which point they curled up together to fall asleep, with Erik lying on his back and Charles tucked into his side. As Erik awakes in the morning he feels his senses spark into life like electricity, prompted into action by the feeling of Charles’ hands slowly trailing up the length of his cock.

Erik has woken up like this once or twice before, when Charles has been feeling especially horny and has decided to wake Erik up with a morning blowjob. But on this occasion it’s not Charles’ mouth Erik can feel against his member, it’s something else entirely…

“NINE INCHES?” Charles exclaims.

It was perhaps unrealistic for Erik to assume that Charles would be willing to just give up without having satisfied his own curiosity… And so, Erik smiles, reaches down to rub Charles’ back comfortingly over the bedsheets, and allows him to continue with his research. Just this once.


End file.
